A broadband amplifier is already known from the publication: IEEE JOURNAL OF SOLID STATE CIRCUITS, VOL. SC-16, NO. 6, DECEMBER 1981 "A GaAs Monolithic Low-noise Broadband Amplifier", John A. ARCHER, Herbert P. WEIDLICH et al.
This publication describes a broadband amplifier which forms a GaAs monolithically integrated circuit. This amplifier circuit comprises two stages which have each an amplifier transistor and a load transistor. The transistors are all of the type that is normally on when there is no gate-source bias voltage. The balance voltage strongly depends on the similitude of the amplifier and load transistors, thus said transistors are identical in each stage and biased with a zero gate-source voltage. For this purpose, on the one hand, the source of the amplifier transistors is connected to ground and their gate is connected to ground through a resistor and, on the other hand, the source and the gate of the load transistors are interconnected and connected to the drain of the amplifier transistors. The circuit further includes in each stage a feedback resistor connected between the drain and the gate of the amplifier transistor of said stage. In this circuit it has been found that the voltage available on the drain of each amplifier transistor is extremely sensitive to the match of the amplifier and load transistors, which leads to a problem when the circuit is to be manufactured in large series, because under these circumstances the characteristic features of the transistors are generally dispersed. Thus the risk is manufacturing losses.